oil level indication / sample port in hermetic compressor

[friocold2008]

Dear fellows:

In the last couple of months I have had to replace a few stuck hermetic piston-type compressors in remote condensing units. Autopsies performed on the dead compressors usually reveal lack-of-oil related problems. Besides the obvious need to find the main reason behind the oil return problem in each case, I´ve always asked myself if there is any reliable method to estimate the crankcase oil level in one of these hermetic compresors. I´ve seen some new Danfoss and Bristol made compressors equiped with oil sightglasses, but the majority of these compressors lack this feature.
Also, does any of you have a preferred method for obtaining an oil sample from the hermetic compressor´s crankcase for acidity testing ? I guess that some sort of sampling port would be useful not only for sampling but also for drainage purposes in case there is a need for an oil change.
Best regards.

[lowcool]

can only say that if system is designed and commissioned correctly you should have no reason to check oil.hermetique offer some with glasses,if you dont mind removing comp you can always fit your own.

[joe magee]

If oil is not returning, it could be a number of problems. First one would be, did you follow proper pipping practices, size, traps etc. Is this a low temp or commercial temp? As far as acid check I use a total test which allows oil entrained vapor to pass through a tube with a special paper inside. All you need is to find a schrader

[friocold2008]

Thank you both lowcool and joe magee for your responses.
To joe: could you please tell me what brand is that total test that only needs the test paper to get wetted by the refrigerant vapor?
To lowcool: your last statement in regards to fit my own oil level sightglass is very interesting...How can this be done?

[D.D.KORANNE]

Oil not returning is a very common problem on a variety of systems. But oil reurn must be ensured first.

System design parameters determine whether one needs an oil separator , oil return suction piping loops its layout etc.

Hence it would save a lot of trouble if system piping practices are followed .

[Eeram]

Remote condensing units should always have oil seperators, even with good piping design.

Hemetic compressors without oil seperators and oil sightglasses are always a risk. Even with a faulty oil seperator that nobody noticed.

The only way to check hermetic compressors without sightglasses for oil levels is to isolate it from the system if there are service valves. Remove the compressor and turn it upside down slowly not to upset the internal mountings. Pour the oil out from the suction port into a measuring jug. Record the amount of oil coming out.

Get specs from supplier and put the correct amount back into the compressor. Make sure it is the right type of oil.

Put back into system and reconnect using good refrigeration practice.

Your compressor will love this treatment with the correct amount of oil, that is also clean now.

[joe magee]

I've worked on a lot of remote condensing units and I have yet to see one with an oil separator. Now racks are a different story. Check your piping ,somethings amiss. Also Make sure you have a full charge.

[lowcool]

oil seps can cause more problems than what their worth only fit them if the application deems it necessary.
you can easily silver solder a sightglass to your dome,something which is not probably recommended from manufacturer as it is a pressure vessel.

[2400martin]

if the broken compressor shows lack on lubrication at points were there is heat generated please send me pictures . may I can help.